Luminaire

ABSTRACT

A luminaire comprising a lamp and a reflector. The lamp has an axis of radiation and the property of emitting a disproportionately large percentage of its luminous flux in an annulus which is contained within a pair of imaginary divergent conical surfaces, each at no more than about 50* to the axis of radiation (100* included angle). The reflector includes reflective cap, side and end surfaces which together form a cavity in which the lamp is placed. The cavity has a plane of symmetry. A longitudinal axis and the axis of radiation lie in the plane of symmetry. The axis of radiation intersects the longitudinal axis at an acute angle. The side and end surfaces are, in cross-section, beaming-directing, and preferably are at least approximations to parabolas, and the flux radiated from the lamp within said annulus impinges upon each of these surfaces.

United States Patent [191 Compton LUMINAIRE Wayne W. Compton, Irvine,Calif.

[73] Assignee: Kim Lighting, Inc., City of Industry,

Calif.

22 Filed: May 15, 1972 211 Appl. No.: 253,591

[75] Inventor:

[52] US. Cl. 240/25, 240/4l.37, 240/73 BC,

. 240/103 [51] Int. Cl. F215 1/10, F21s 3/10, F2ls 13/10 [58] Field ofSearch 240/25, 41.37, 73, 240/103 [5 6] References Cited UNITED STATESPATENTS 3,179,793 4/1965 Franck 240/25 3,189,739 6/1965 McPhail...240/25 3,350,556 /1967 Franck et al 240/ 440/115 0 @Zf/VD) ZO/VG/TUD/NALJ AXIS 1 WL 7 WL [451 Jan. 15, 1974 Primary Examiner-Samuel 5. MatthewsI Assistant Examifier- Richard A. Wintercorn Att0rney-D. Gordon Angus etal.

[5 7] ABSTRACT A luminaire comprising a lamp and a reflector. The lamphas an axis of radiation and the property of emitting adisproportionately large percentage of its luminous flux in an annuluswhich is contained within a pair of imaginary divergent conicalsurfaces, each at no more than about to the axis of radiation includedangle). The reflector includes reflective cap, side and end surfaceswhich together form a cavity in which the lamp is placed. The cavity hasa plane of symmetry. A longitudinal axis and the axis of radiation liein the plane of symmetry. The axis of radiation intersects thelongitudinal axis at an acute angle. The side and end surfaces are, incrosssection, beamingdirecting, and preferably are at leastapproximations to parabolas, and the flux radiated from the lamp withinsaid annulus impinges upon each of these sur faces. 1

32 Claims 12 Drawing Figures PATENTEBJAH 1 51974 SHEET 8 [IF 5 LUMINAIREThis application relates to luminaires, and in particular to thecombination of a lamp and a reflector which have interrelated physicalproperties.

As requirements for illumination of large areas have multiplied, so toohave the consequences of the shortcomings of existing devices for thispurpose, which depend heavily upon refracting bodiesfor their control ofthe light. One objection which is heard with increasing frequencyconcerns visual pollution of the environment caused by glare lightscattered by conventional luminaires. Not only is the background glowbrightened by this glare, but the stray light in itself is unpleasantand even potentially harmful, such as by causing windshield glare. Also,it reduces the contrast between an illuminated object, such as a personwalking along a sidewalk, and the background. This endangers the person,because he is, in effect, less visible. Such contrast should be made aspronounced as possible. As still another objection, the stray lightcauses pupillary constriction. Such constriction limits the ability ofthe human vision system to identify illuminated objects.

The increased power consumption needed in order to provide a specificlight intensity at the surfaces to be illuminated, when light is wastedby glare, raises energy bills.

Yet another disadvantage of the prior art resides in the tendency ofexisting illumination means to form hot spots, or areas of excessivelighting, while leaving other areas poorly lighted, all within theintended distribution region of the luminaire.

It is an object of this invention to provide a luminaire which canilluminate substantial areas with much closer approximationto uniformityof illumination'than has been possible with prior art reflectors orrefractors.

It is another object of this invention to provide a luminaire which hasrelatively sharp cut-offs of illumination, thereby concentrating itslight in a restricted, intended area.

' lines which, in an axial plane, diverge from the normal to the axis ofradiation by no more than about 50. The reflector has a longitudinalaxis and a plane of symmetry which includes both the longitudinal axisand the axis of radiation. The reflector forms an open, inwardly concavecavity in which the lamp is placed. The cavity is bounded, at least inpart, by the following reflecting Still another object of this inventionis to accomplish the foregoing objectives with the use of commerciallamps which are readily available on the market, and which can beenclosed in relatively small enclosures so the luminaire constitutesonly a minimum visual disruption to the surroundings.

Yet another object of the invention is to provide a luminaire whosedistribution of light can be asymmetrical-illuminating regions fartherto one side of the luminaire than to the other-while utilizing areflector whose bottom edge is horizontal. With the reflector of thisinvention, asymmetric distribution does not require tilting thereflector, or the use of a refractor, and therefore the observer doesnot see a bright light source as he views the luminaire from the side orfront. This is one of the major advantages of this invention. With it,one can illuminate an area farther removed from the luminaire on oneside than on the other, and still the emitting region is not tilted soas' to be visible as a bright area in the sky.

This invention provides an elegantly simple luminaire which in itself isinoffensive in appearance, which illuminates areas withconsiderableconsistency without appreciable stray glare, and which isreadily adjusted to provide for different configurations of illuminationof areas beneath it.

surfaces: a) a cap surface which overlays the cavity and extendsgenerally along and transverse to the said longitudinal axis; b) a pairof concave side surfaces, one on each side of the plane of symmetry,each intersecting the cap surface and extending generally along saidlongitudinal axis; and c) a concave end surface which intersects andinterconnects both side surfaces and the cap surface. These surfaces arespecularly reflective over the majorportion of their areas. The axis ofradiation forms an acute angle with the longitudinal axis. The fluxwithin the annulus impinges upon each of the said surfaces.

According to a preferred but optional feature of the invention, someportions of the cap surface are modifled by light-diffusing facets. v

According to still another preferred but optional feature of theinvention, the section lines 'of the side and end surfaces are beamcontrolling, and in gross are at least approximations to parabolas.

According to still another preferred but optional feature of theinvention, the said section lines comprise the arcs of at least twocircles of different radius.

The aboveand other features of this invention will be fully understoodfrom the following detaileddescription and the accompanying drawings inwhich:

FIG. 1 is a side view, principally in axial cross-section of thepresently preferred embodiment of the invention taken along its plane ofsymmetry;

FIG. 2 is a bottom view of FIG. 1, looking upwardly into the cavity;

FIG. 3 is a cross-section taken at line 3-3 of FIG. 2;

FIG. 4 is a fragmentary cross-section taken at line 4-4 of FIG. 1;

FIG. 5 is a cross-section taken at line 5-5 of FIG. 1; and

FIGS. 6-12, inclusive, are sketches that are explanatory of certainfeatures of the invention.

A luminaire 20 according to the invention is shown in FIG. 1. It isfitted into a housing 21 which, because of the compactness of theelements it contains, may be made as a rectangular parallelopiped. Thishousing may readily be attached to a pole or some other kind of support,such as a wall.

It is desirable, and in general will be the situation,

that the lower surface 22 of the housing will be parallel to the ground.It is a particular advantage of this invention that such an arrangementcan be made. Conventional luminaires accomplish asymmetricaldistributionof light by tilting the luminare and/or reflector, or by usingrefractors. In so doing, their refractors or reflectors, or both, aredirectly exposed to and visible by the observer, and become a primesource of nighttime visual pollution. Such refractors, reflectors, orboth are a common sight on the night-time skyline. The term asymmetricaldistribution" means that more light is directed to one side of a planenormal to the longitudinal axis than to the other side of the axis.

The housing includes four sides 23, a top 24, and an open base 25. Thebase has an aperture 26 in which a transparent pane 27 is fitted. Thepane is readily removable from its supporting frame 28. The frame isattached to the housing.

Auxiliary control equipment 30 is fitted inside the housing. Suchequipment may include ballast, capacitors, circuit boards, switches andleads. Connections are made to the auxiliary control equipment and fromthis equipment to the lamp socket. The foregoing are all conventionalelements and require no detailed description here, because they form nopart of the invention.

A lamp 35 is supported inside a cavity 36 formed by a reflector 37. Thereflector is supported at its edge 38 by the housing. It fills aperture26, and flux from the lamp is emitted through the aperture. The lamp andreflector will now be described in further detail.

Lamp 35 is of a conventional type used in the illumination field. Theillustrated lamp is a 175 or 250 watt mercury vapor lamp. As otherexamples, there may instead be used high pressure sodium lamps ormetallic halide lamps. All of these lampshave a socket end 40 which isto be screwed into a socket 41, and a glass envelope 42. They also havean axis of radiation 43 which is linear. A feature of the class of lampuseful in this invention is that, with respect to the axis of radiationand a theoretical center 44 thereon, there is an annulus generatedaround the lamp axis which contains a disproportionately largepercentage of the luminous flux emitted by the lamp compared to thepercentage of the flux emitted outside this annulus. For example, suchan annulus is imaginary generated by a pair of generator lines 46, 47which diverge from from the normal 48 (a normal plane) to the axis ofradiation by angles 49, 50 which are about 50. In most lamps of the typedescribed, about 75 percent of the luminous flux is emitted in such anannulus in which the total of angles 49 and 50 is less than about 100".This means that relatively little light is emitted rearwardly toward thesocket end, or forwardly toward the tip end of the lamp. The candlepowerdistribution of this type of lamp is shown in FIG. 8. The distance ofthe solid line 66 from the center 67 of the lamp graphically illustratesthe intensity of lumination at the respective angular position aroundthe center, the distance of line 66 from the center indicating therelative intensity at the respective angle. A greater distance from thecenter in this graph indicates a greater intensity.

The term axis of radiation defines an axis which is related to thepattern of light intensity emitted by the lamp. It is a central axisaround which the aforesaid annulus is generated. In a conventional lampwherein an arc tube is the light source, the intersections of generatorlines 46 and 47 with the axis are spaced apart by an appreciabledistance, perhaps an inch or more, and the annulus will not have a pointcenter on the axis, but rather a line coincident with the axis. If thelamp were a theoretical point source, then the two lines would intersectat the axis of radiation. In either case, the axis would be the same,because it is referred to the pattern of emission, and not to the shapeor nature of the light source itself.

For convenience, the theoretical center 44 is referred to. In apractical arc tube lamp, the center 44 is located at the mid-point ofthe envelope.

In order to provide different illumination patterns on the pavement witha given reflector, means is provided for supporting the lamp atpredetermined locations along both the axis of radiation and thelongitudinal axis of the reflector. For example, socket 41 is attachedto nipple 51 and held to a mounting bracket 52 by lock nuts 53. Thebracket has an elongated slot 54a. The lock nuts can be loosened toenable the nipple to be axially shifted to move the lamp axially, andvertically shifted in the slot to 'move the lamp vertically. The lampcan thereby be moved to various positions in the reflector, and the locknuts tightened to hold itin the selected location. Two exemplarypositions for the lamp are shown in the drawings, which will provide twodifferent patterns of illumination. This adjustment feature also enableslamps of different sizes to be received and placed in selectedlocations.

The solid line socket position will hold the lamp in the location shownby solid line, and retraction and downward movement of the nipple willmove the socket to the dashed line position where the envelope will beheld in the position as shown by the dashed line with its center at 44ainstead of at 44. It will thereby be seen that the flux within theannulus can be made to impinge differently on the reflector, dependingon the location of the lamp in the cavity. Other means for locating thelamp in different positions may readily be devised, such as by stackingup adapter plugs between the lamp and a stationary socket. The lamp isheld so that its axis of radiation remains in the plane of symmetry 54of reflector 37. The plane of symmetry is the plane of FIGS. 1 and 3.The plane of symmetry shown is also a central plane. As will laterbecome clear, the plane of symmetry is, in every case, a central plane.However, in every case, the central plane will not necessarily be aplane of symmetry, because the side surfaces are not necessarilyidentical, although they are identical in the preferred embodiment. Agiven lamp is also preferably supported so that its center 44 remains ata predetermined elevation when the position of the lamp in the reflectoris changed.

A shroud 55 covers the mounting bracket and much of the socket. Itserves to protect leads 56 from the heat of the lamp, and constitutes anesthetically pleasing envelope.

With initial reference to FIG. 2, the reflector includes a cap surface60, a first side surface 61, a second side surface 62, and an endsurface 63. The side surfaces and end surface all intersect and blendinto the cap surface. As can be seen in FIGS. 1 and 2, the cap surfaceoverlays the cavity and extends transversely relative to thelongitudinal axis 64 of the reflector. The longitudinal axis lies in theplane of symmetry and extends in a direction which will ordinarily beparallel to the ground surface or to whatever surface is beingilluminated. It extends midway between the two side surfaces. Itforms anacute angle 65 with axis of radiation 43. Ordinarily, this angle will beon the order of about 20. The cap, side and end surfaces define aninwardly concave cavity in which the lamp is placed. The cavity opensonto a base plane, which may be defined as the plane of pane 27. Thebase plane is parallel to the longitudinal axis, and in usual usage ofthe reflector, it will be parallel to the ground. The reflector need notbe tilted to give an asymmetrical distribution.

To secure the desired asymmetrical distribution, it is necessary toprovide surfaces which will specifically reflect light to each part ofthe illuminated area, and in a pattern wherein the intensity isreasonably uniform over the total illuminated region. As with anyluminaire system, there is no abrupt fall-off from bright light to totaldark in the sense of blackness in immediate contiguity withillumination. However, in contrast with conventional luminaires, a sharpfall-off from an acceptable level of illumination to a level ofillumination which is not appreciably bright does occurwithin aremarkably small space. In order to accomplish this objective,reflecting surfaces with beam-forming properties.

The configurations of the foregoing surfaces will now be described.First, it will be remarked again that the annulus of the lamp is shownas though it originated at a central point 44, while in a practical lampthe generator lines 46 and 47 will be separated from each other by asubstantial distance along the axis of radiation because of the extendedlength of the arc tube of the lamp. However, whether the lamp has apoint source or a line source, the geometry is substantially as shown. Apoint source is used for conveniencein disclosure.

The annulus shown relates to the position of the lamp illustrated insolid line. In the illustration, if the lamp were about 8 inches longfrom the end of the socket to the tip of the glass envelope, theintersections of generator lines 46 and 47 with lamp axis 43 would beabout 2 inches apart, thereby making the annulus longer than shown, inwhich case light within the annulus would strike a larger area of thesurfaces. The luminous flux within the annulus, whatever the axiallength, will impinge upon each of the cap surface, the side surfaces,and end surface 63. Those portions of these surfaces which intersect theannulus will therefore determine the distribution of the majorproportion of the luminous flux of the lamp. Some of the flux will, ofcourse, pass directly from the lamp through aperture 26 withoutreflection.

The cap surface overlays the lamp. It is advanta geous, but notnecessary, to incorporate a plurality of down-light diffusing facets 68into this surface. These facets serve to scatter light rather than tofocus it, and perform two useful functions. One such function is toreduce hot spots on the ground beneath the reflector. Hot-spots arelocal regions which are appreciably brighter than neighboring regionswithin the area being illuminated. The scattered light tends to even outthe distribution. The other advantage inscattering some of the lightfrom the cap surface is that the amount of energy reflected back intothe arc tube is reduced. Energy reflected into the arc tube shortenslamp life.

The preferred shape of the facets is, as shown, the convex polar sectionof a sphere. However, concave polar sections, and other concave andconvex shapes may be used instead, to the same advantage.

Facets 68 do not scatter the light beyond the field limited by thereflector, because of the cut-off effect of the outer edge of theaperture 26. They do, however, appreciably scatter the light reflectedfrom the cap surface so that there are no areas of disproportionatelygreat intensity derived from reflection on that surface alone. The lightfrom the reflector is therefore softened.

The side and end surfaces are beam-forming in nature. Preferably, eachforms at least a gross approximation to a parabola for the purpose ofthrowing a directed beam sideward relative to the perpendicular, whilethe cap surface serves more to illuminate the area more directly underthe luminaire. To form true parabolic surfaces which are appropriate tothe geometries involved not only involves considerable computation, butalso a considerable expense in tooling. It has been found that optimumlight distribution can be derived from surfaces having area's formed bycircularly arctiate generators, there being more than one such generatorfor each surface, their radii being different. Such a constructioncreates a light distribution which is at least an approximation to thatcreated by a true parabolic surface, and in some respects appears to besuperior for the purposes of this invention.

' Accordingly, and as can best be seen in FIG. 5, surface 61 is formedby a first radius and a second radius 71, while surface 62 is formed. bya first radius 72 and a second radius 73. These surfaces are mirrorimages of one another, and the dimensions of one are the dimensions ofthe other. Inboth cases, the surface portions formed by the first radiiare of larger radius and closer to the open end of the cavity, while thesecond radii are shorter than the first radii and lie farther within thecavity. The location of the centers'of these radii are shown in thefigure. A fairing or transition radius 74 is formed between the capsurface and the side surfaces. It has no necessary correlation to theparabolic approximation, although it may have, if desired. It isprimarily intended to constitute a smooth transition between the sidesurfaces and the cap surface.

Surfaces 61 and 62 preferably are in the form of bent planes, andaccordingly, the cross-sections shown in FIG. 5 are generators whichgenerate the respective surfaces by being moved parallel to, and at aconstant distance from, the longitudinal axis. However, it willoccasionally be found that, instead of using shapes which lieprincipally at constant distances from the longitudinal axis, somecurvatures may be advantageously introduced into surfaces 61 and 62,such as by bowing them outwardly. Such modifications remain within theconcept of the invention.

End section 63 is'preferably formed as a surface of revolution revolvedaround a central axis 80, which axis lies in the plane of symmetry andnormal to the longitudinal axis. Surface 63 has a radius C from thiscentral axis, details of which will be found in the accompanying tables.The generator line 81 is shown in FIG. 3, and in this surface, as wellas in the other surfaces defined as generator surfaces, the term is usedin a geometric sense of a line moved through space to generate asurface. The curvatures of surfaces 40 and 63 as shown are identical atthe plane of symmetry, and the dimensions given for surface 40 areidenticalto those of surface 63, and vice versa. Full details of onlyone are is shown in order to simplify the drawings. If, instead ofhaving the light reflected identically by each of the side surfaces 61and 62, it is desired to have one throw its light farther than theother, then the curvatures of the two side surfaces may not beidentical, but instead may be differently curved. Such a construction isstill within the concept of the invention. In such case, a plane ofsymmetry will not exist between two mirrorimage surfaces, but the planewould more properly be described as a central plane, i.e. the plane inwhich the axis of radiation lies, and the terms central plane and planeof symmetry are used interchangeably herein, as appropriate.

As will be seen in the drawings, the generator line 81, and thereforethe resulting surface 63 in vertical section, is an approximation to aparabola and is formed by a first radius 82 and a second radius 83,which radii are preferably, but not necessarily, identical to radii70-73, respectively, and located at substantially the same elevationsrelative to the open end of the cavity. Therefore, the end surfaceconstitutes a substantial continuation of side surfaces 61 and 62.Central region 85 of end surface 40 is not necessarily a curve. Instead,it may constitute a bent plane with the curvature shown in FIG. 3, andit is connected to the side surfaces by transition regions 86, 87 whichare formed by radii and curves as shown in the drawings. Regions 85, 86and 87 are not substantially important to the reflectors performance forthe reason that, with respect to the heavy dashed line identified asedge 88 of light-absorbing region, those portions towardthe socket end,to the left of that edge line 88, are painted flat black as is thesocket shroud. Accordingly, substantially no reflection occurs from thatend. Instead, substantially all reflection occurs from the side, end andcap surfaces.

One reason that these regions 8587 are relatively unimportant is thatlittle lamp flux impinges upon them due to the nature of thedistribution of the flux from the lamp itself. A reason for paintingthese areas black is that otherwise they would reflect light toward thehouse side, frustrating one objective of the luminaire, which is to castits light away from a pole or house, and not toward it, from ahorizontal aperture.

The detailed construction of the presently preferred embodiment ofreflector is shown in the following table. All dimensions are in inches,and the identification of dimensions relate to those which are shown inthe accompanying drawings.

RADIUS DIMENSIONS RAD. B 16.34 16.34 16.28 16.18 16.03 15.71 15.25

OTHER DIMENSIONS RAD. B 7.68 RR 7.87

TT 7.515 UU 12.312 VV 7.515 WW 12.312

RAD. C 6.00 6.00 5.96 5.87

RAD. D 2.00 2.00 1.96 1.78 1.71 1.40 0.93 0.81 0.62 0.50

RAD. A 5.62 5.62 5.59

WL No. AA 1.656 BB 12.00 CC 6.00 DD 6.312 E 8.00

FF 4.312 GG 1.218

RAD. A HH 2.375 .1! 0343 XX 4.68 LL 5.34 MM 6.28 NN 6.93 PP 7.40

RAD. C XX 1.50 YY 1.218 22 2.375 AB 1.06 AC 0.375 AD 2.50 A15. 2.00

RAD. D AF 0.62 AG 9.37s AH 1.906 AJLSO AK 2.00 AL 1.25

The location of the socket is moved as previously discussed, to placethe lamps center at the location required for a respective distributionof light.

Some considerations and features of this luminaire are shown in FIGS.612. For convenience, there has been set up a reference to a house sideand a street side. Of course, there need not be a house or a street.Instead, the luminaire might be used to illuminate a parking lot orother open area far from a building. What is shown is a situation wherethe light distribution on one side of the luminaire itself extends to alesser horizontal distance than on the other, and in which the shape ofthe illuminated region is quite carefully controlled, with sharp cutoffsat the edges, there being a substantially consistent and relativelyconstant illumination throughout the illuminated area, and a relativelysharp rate of decrease of brightness as one moves away from the-areaintended to be illuminated. This is accomplished, while using ahorizontal aperture, and no refractors, thereby greadly reducing strayglare.

As to the illumination caused by this luminaire, initial attention iscalled to FIGS. 6 and 7. In these figures there are shown two types ofdistributions which are defined as ANSI Type II and Type III,respectively. The Type II illumination casts a lesser throw onto thestreet side than the Type III illumination. In both cases, theillumination on the house side is about the same. Other patterns can bemade by shifting the lamp along its axis, or by varying the shape and/orsize of the reflector. The luminaire is shown in both figures, and theilluminated area is shown in shaded linewith boundaries 91, 92respectively. These boundaries indicate the outer limit of substantialillumination from the luminaire as cast upon the ground. A pole93isschematically shown holding the luminaire above the ground.

The two different patterns were obtained by the use of the samereflector and lamp. The pattern of FIG. 6 was changed to that of FIG. 7by shifting the lamp horizontally toward socket end 40. This was done bymoving the lamp socket toward the socket end, and shifting the socketupwardly in slot 541:. The sideward throw was not appreciably changed.To change the sideward throw, one would move the lamp center of thevertically. Various combinations of movement are made to form otherillumination patterns.

FIG. 8 shows the candlepower distribution of the lamps disclosed above.The heavy lines 66 indicate the candlepower intensity at the respectiveangles. It will be observed that a disproportionately small part of theradiation is radiated outside of the annulus.

FIG. 9 shows the interaction between the lamp and the reflector. Thecandlepower curve 66 of the lamp by itself is shown in dashed line,while the resulting candlepower curve of the lamp plus reflector isshown by line 95. It will be seen that the reflector has modified theflux distribution of the lamp so that a minimum of light is projectedtoward the house side, while the major portion of light is efficientlyprojected on the street side where it is needed. This is one of theimportant consequences of the combination of the particular lamp andreflector, and still can be secured with a horizontal aperture.

FIGS. 10 and 11 show the effect of shifting the lamp along its axis ofradiation. In FIG. 10, the Type III distribution of FIG. 7 is shown. Inthis condition, the lamp is in the solid line position of FIG. 1, Le.closer to the pole end itself. In this case, it will be found that themajor proportion of the flux departs in a band 97, as shown in FIG. 10,and that this band will intersect the ground in the manner shown in FIG.7.

In FIG. 1 l, the center of the lamp 35 is in the dotted line positionshown in FIG. 1, and in this case, the major proportion of the fluxdeparts in band 98, whose intersection with the ground is that shown inFIG. 6.

FIG. 12 shows a section similar to that of FIG. 5, the section beingtaken in a plane normal to that of the longitudinal axis. This figureillustrates the cut-off effect of the bottom edge 38 of reflector 37. Aswill be seen, the lower edge acts as a cut-off for direct light from thelamp, and reflected light from the various surfaces will besubstantially confined within the region defined by edges such as themajor cut-off edge 99. The scattering action of the facets is shown byray 100, whose reflected direction is indeterminate, but which islimited by the cut-off edge 99. i

The reflector shown is not a true parabola, but it is an approximationto one. A true parabola could be used. It would reflect a collimatedbeam of light toward the pavement. The directed beam produced by theillustrated reflector is not truly collimated, but is a projected beam,even though it is not a bundle of parallel rays, and tends to spread thelight somewhat, as contrasted with a bundle of strictly parallel rays.In this luminaire, the beam directing effect is used to project a beamaway from the surface. Beams are sent to both sides and away from thehouse. The blackened surface prevents light from being reflected to thehouse side. Light reflected from the surfaces and direct radiation fromthe lamp illuminate the area directly beneath the aperture and to eitherside and to the street sidewithin focus has been found useful, becauseit does appear to.

give a more even distribution of light. The effect of this arrangementis shown in FIG. 12, where two beams 110, 111 are shown emanating fromthe two circular portions 112, 113 of side surface 61, that are formedby radii 71 and 70, respectively. Of course, these beams .will not bestrictlycollimated, because the cylindrical surfaces will tend to spreadthe beam, but the center of the lamp is spaced from the respectivesection between the center and the surface, so that at least some beamdirecting of the radiation from the lamp is accomplished. The termbeam-forming or beam-directing is used to describe the function of thereflecting surfaces in forming a beam of light. The termfspecular isintended to define the function of reflection of light, in contrast tothe dull and diffuse illumination produced by a matte surface.

To change the light distribution pattern, the lamp is shifted so as toradiate more or less light on the different portions of the reflector,and at different positions relative to the quasi-focus" of thereflector, i.e., the location of the focus of the parabola which thesections approximate. It should be borne in mind that these lightsources are not true points or lines, but physical structures ofsubstantial length and width. Therefore, the definition of location ofthe axis of radiation relative to the quasi-focus must be somewhatapproximate. It may be said in general that a downward displacement ofthe lamp will tend to increase the lateral throw. A displacemerit towardthe end surface has a lesser effect than downward displacement, but doescause a farther throw onto the street side (see FIGS. 10 and 11). Inmost practical applications, the axis of radiation will pass relativelynear to the quasi-focus of the approximated parabola, and in thepreferred form, will intersect this focus somewhere along the length ofthe axis of radiation. The approximated parabola can best be drawn bylaying a french curve as close as possible to the cylindrical sections.

The dimensional notations WL in the drawings relate to the term waterline frequently used in die-making operations, and the dashed linesfollowing them Is the number of inches up from the bottom edge 38. Alldimensions are referred to this water line. Thus, WL l means ahorizontal section taken I inch above the lower edge of the reflector.

The reflector shown is simple in shape, readily developed by a tool anddie man, and easily produced in common and practical manufacturingoperations. It is surprisingly effective in its control of high angleglare light and of distribution patterns on the ground. The

different wattage. The construction is adapted to use with any suitablelamp of the class described, and may readily be scaled up or down as tosize. The entire system may be placed in a rectangular enclosure ofelegant simplicity.

Attention is further called to the fact that the SOCItCt end of the lampis nearest the area being illuminated, and does not lie in the path ofuseful light. I

This invention is not to be limited by the embodiment shown in thedrawings and described in the description, which is given by way ofexample and not of limitation, but only in accordance with the scope ofthe appended claims.

I claim:

1. In combination: a lamp which emits visible light, said lamp having anaxis of radiation and the property of emitting a disproportionatelylarge percentage of its luminous flux in an annulus bounded by a pair ofsur faces of revolution generated around the axis by generator lineswhich, in an axial plane, diverge from the normal to the axis ofradiation by no more than about 50; and a reflector having alongitudinal axis, an imaginary central plane which includes saidlongitudinal axis and axis of radiation, and an open, inwardly concavecavity in which the lamp is placed, said cavity opening at a base planeparallel to the longitudinalaxis, said cavity being bounded, at least inpart, by the following reflecting surfacesf a. a cap surface whichoverlays the cavity, and extends generally along and transverse to saidlongitudinal axis;

b. a pair of concave side surfaces, one on each side of the centralplane, intersecting the cap surface, and extending generally along saidlongitudinal axis; and

c. a concave end surface intersecting and interconnecting both sidesurfaces and the cap surface, said surfaces being specularly reflectiveover the major portion of their areas, and having a beam-formingproperty with respect to light emitted by the lamp, the axis ofradiation forming an acute angle with the longitudinal axis, and theflux within said annulus impinging upon each of said surfaces.

2. A combination according to claim 1 in which the cap surface issubstantially planar.

3. A combination according to claim 2 in which some portions of the capsurface are modified by lightscattering facets.

4. A combination according to claim 1 in which the section-lines of theside which are formed by intersection with said surfaces by a planenormal both to the longitudinal axis and to said side surfaces, and inwhich the section-line formed by intersection of the end surface and aplane which includes a line in said central plane that is normal to thelongitudinal axis, are at least approximations to parabolas.

5. A combination according to claim 4 in which said section linescomprise the arcs of at least two circles of different radius.

6. A combination according to claim 1 in which said side surfaces aregenerated by a concave arcuate generator line lying in a plane normal tothe longitudinal axis and moved in a substantially straight lineparallel to said longitudinal axis, said generator line being at leastan approximation to a parabola.

7. A combination according to claim 6 in which said generator linecomprises the arcs of at least two circles of different radius.

8. A combination according to claim 1 in which the end surface isgenerated by a concave arcuate generator line which lies in a planeinclusive of a central axis in said central plane which is normal to thelongitudinal axis, and which generator line is moved through a circularare around said central axis, the generator line being at least anapproximation to a parabola.

9. A combination according to claim 8 in which said generator linecomprises the arcs of at least two circles ofdifferent radius.

10. A combination according to claim 6 in which the end surface isgenerated by a concave arcuate generator line which lies in a planeinclusive of a central axis in said plane of symmetry which is normal tothe longitudinal axis, and which generator line is moved through acircular are around said central axis, the generator line being at leastan approximation to a parabola.

11. A combination according to claim 10 in which each of said generatorlines comprises the arcs of at least two circles of different radius.

12. A combination according to. claim 11 in which the cap surface issubstantially planar.

13. A combination according to claim 12 in which some portions of thecap surface are modified by lightand energy-scattering facets.

14. A combination according to claim 1 which further includes socketmeans for holding said lamp, said socket means being adapted to hold thelamp at different axial locations along said lamp axis.

15. A combination according to claim 11 which further includes socketmeans for holding said lamp, said socket means being adapted to hold thelamp at a plurality of different axial locations along said lamp axis.

16. A combination according to claim 1 in which the end of the cavityopposite the said end surface is substantially nonreflective.

17. A combination according to claim 8 in which the end of the cavityopposite the said end surface is substantially reflective.

18. A combination according to claim 1 in which the boundaries of thesurfaces at the open edge of the cavity are coplanar.

l9. A combination according to claim 11 in which the boundaries of thesurfaces at the open edge of the cavity are coplanar.

20. A combination according to claim 1 in which a support holds thereflector above the ground, and the greater area of illumination extendsaway from the projection of the support on the ground, there furtherbeing provided'a socket to receive and support the lamp, there being asocket at the end of the reflector away from the support, and thereflecting end section being the closer to thesupport.

21. A combination according to claim 1 in which the socket end of thelamp is deeper in the cavity of the reflector than the free end of thelamp, and in which the socket end of the lamp is the end farther removedfrom the said end surface. V

22. A reflector for forming a field of radiated light from a lamp of thetype which emits visible light, said lamp having an axis of radiationand the property of emitting a disproportionately large percentage ofits luminus flux in an annulus bounded by apair of surfaces ofrevolution generated around the axis by generator lines which, in anaxial plane, diverge from the normal to the lamp axis by no more thanabout 50, said reflector having a longitudinal axis, a central planewhich includes said longitudinal axis and lamp axis, and an open,inwardly concave cavity in which the lamp is placed, said cavity openingat a base plane parallel to the longitudinal axis, said cavity beingbounded, at least in part, by the following reflecting surfaces:

a. a cap surface which overlays the cavity, and extends generally alongand transverse to said longitudinal axis;

b. a pair of concave side surfaces, one on each side of the centralplane, intersecting the cap surface, and extending generally along saidlongitudinal axis;

c. a concave end surface intersecting and interconnecting both sidesurfaces and the cap surface, said surfaces being specularly reflectiveover the major portion of their areas; and means for supporting saidlamp in the cavity, the said surfaces having a beam-forming propertywith respectto light emitted by the lamp, the means being so disposedand arranged as to support the lamp so that its axis of radiation formsan acute angle with the longitudinal axis, and the flux within saidannulus impinges upon each of said surfaces.

23. A reflector according to claim 22 in which the cap surface issubstantially planar.

24. A reflector according to claim 23 in which some portions of the capsurface are modified by lightscattering facets.

25. A reflector according to claim 22 in which the section-lines of theside and end surfaces which are formed by intersection with saidsurfaces by a plane normal both to the longitudinal axis and to saidside surfaces, and in which the section-line formed by intersection ofthe end surfaces and a plane which includes a line in said central planewhich is normal to the longitudinal axis are at least approximations toparabolas.

26. A reflector according to claim 25 in which said section linescomprise the arcs of at least two circles of different radius.

27. A combination according to claim 22 in which said side surfaces aregenerated by a concave arcuate generator line lying in a plane normal tothe longitudinal axis and moved in a substantially straight lineparallel to said longitudinal axis, said generator line least anapproximation to a parabola.

28. A combination according to claim 1 in which the central plane is aplane of symmetry.

29. A combination according to claim 4 in which the being at 5 centralplane is a plane of symmetry.

Page 1 of 2 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PatentNo. 3,786,248 Dated January 15, 1974 Inventor(s) WAYNE COMPTON It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

Col. 2, line 10 change "plane of symmetry" to -imaginary central plane(which may be a "plane of symmetr Col. 2, line 18 change "plane ofsymmetry" to --centralp Col. 2, line 42 change "plane of symmetry" toe-imaginary central plane-- Col. 3, line 37 "imaginary generated by apair" should read -generated by a pair of imaginary--= Col. 4, line 33plane of symmetry" should read --=eentral p ane-- Col. 4, line 34 after"54" insert "which in this example is also a plane of symmetry-- Col. 4,line 57 before "plane" insert --central plane, which' in this example isalso a-- Col. 4, line 57 insert a comma after "symmetry" Col. 6, line 65plan: 0:5 symmetry' should read -=-"plane of i symme ry Col. 7, line 1'central plane should read --"central plane" Col. 7, line 2 plane ofsymmetry should read --"plane of I symmetry"-- Col. 7, line 3 after"appropriate." insert --The plane is :ll-maglnaryn-l n n Col. 7, line 14bent plane should read bent plane M Col, 9, line 34 "ermitted" shouldread permitted==- Col. 9, line 50 'be m-directing' should read--"beam-=direct= ing Col.v 10, line ll 'WL' should read --"WL"-- dPatent No.

Col. ll, line .9 (Claim 4, line 2) Col. 11, line 12 (Claim 4, line 4)Col. 11, line 12 (Claim 4, line 5) Col. ll, line 42 (Claim 10, line 4)Col. 12, line 58 (Claim 25, line 2) Col. 12, line 61 (Claim 25, line 5)Col. 12, line 61 (Claim 25, line 5) [SEAL] RUTH C. MASON ArrestingOfficer Dated January 15, 1974 Inventor s) WAYNE W COMPTON It iscertified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

after "side" insert --surfaces-- cancel "in which" "section-line" shouldread --section-lines-- change 'pla ne of symmetry" to --cen'tralplane--cancel "and end" cancel ''in which" "section-line" should read--section-lines--- Signed and Scaled this Fifteenth Day of February 1977A ttest:

C. MARSHALL DANN Commissioner ofPatenls and Trademarks UNITED STATESPATENT OFFICE CERTIFICATE OF CORRECTION Patent 5.786.2 6 Dated January15. 197A Inventor(g) Wayne W. COInp'tOn It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

Column 'l, line 52, "is" should read can be O Sugncd and Scaled thusTwenty-ninth Day of March 1917 [SEAL] O Arrest:

RUTH c. MASON c. MARSHALL DANN Anesting Officer Commissioner oj'PaIentsand Trademarks O

1. In combination: a lamp which emits visible light, said lamp having anaxis of radiation and the property of emitting a disproportionatelylarge percentage of its luminous flux in an annulus bounded by a pair ofsurfaces of revolution generated around the axis by generator lineswhich, in an axial plane, diverge from the normal to the axis ofradiation by no more than about 50*; and a reflector having alongitudinal axis, an imaginary central plane which includes saidlongitudinal axis and axis of radiation, and an open, inwardly concavecavity in which the lamp is placed, said cavity opening at a base planeparallel to the longitudinal axis, said cavity being bounded, at leastin part, by the following reflecting surfaces: a. a cap surface whichoverlays the cavity, and extends generally along and transverse to saidlongitudinal axis; b. a pair of concave side surfaces, one on each sideof the central plane, intersecting the cap surface, and extendinggenerally along said longitudinal axis; and c. a concave end surfaceintersecting and interconnecting both side surfaces and the cap surface,said surfaces being specularly reflective over the major portion oftheir areas, and having a beam-forming property with respect to lightemitted by the lamp, the axis of radiation forming an acute angle withthe longitudinal axis, and the flux within said annulus impinging uponeach of said surfaces.
 2. A combination according to claim 1 in whichthe cap surface is substantially planar.
 3. A combination according toclaim 2 in which some portions of the cap surface are modified bylight-scattering facets.
 4. A combination according to claim 1 in whichthe section-lines of the side surfaces which are formed by intersectionwith said surfaces by a plane normal both to the longitudinal axis andto said side surfaces, and the section-lines formed by intersection ofthe end surface and a plane which includes a line in said central planethat is normal to the longitudinal axis, are at least approximations toparabolas.
 5. A combination according to claim 4 in which said sectionlines comprise the arcs of at least two circles of different radius. 6.A combination according to claim 1 in which said side surfaces aregenerated by a concave arcuate generator line lying in a plane normal tothe longitudinal axis and moved in a substantially straight lineparallel to said longitudinal axis, said generator line being at leastan approximation to a parabola.
 7. A combination according to claim 6 inwhich said generator line comprises the arcs of at least two circles ofdifferent radius.
 8. A combination according to claim 1 in which the endsurface is generated by a concave arcuate generator line which lies in aplane inclusive of a central axis in said central plane which is normalto the longitudinal axis, and which generator line is moved through acircular arc around said central axis, the generator line being at leastan approximation to a parabola.
 9. A combination according to claim 8 inwhich said generator line comprises the arcs of at least two circles ofdifferent radius.
 10. A combination according to claim 6 in which theend surface is generated by a concave arcuate generator line which liesin a plane inclusive of a central axis in said central plane which isnormal to the longitudinal axis, and which generator line is movedthrough a circular arc around said central axis, the generator linebeing at least an approximation to a parabola.
 11. A combinationaccording to claim 10 in which each of said generator lines comprisesthe arcs of at least two circles of different radius.
 12. A combinationaccording to claim 11 in which the cap surface is substantially planar.13. A combination according to claim 12 in which some portions of thecap surface are modified by light- and energy-scattering facets.
 14. Acombination according to claim 1 which further includes socket means forholding said lamp, said socket means being adapted to hold the lamp atdifferent axial locations along said lamp axis.
 15. A combinationaccording to claim 11 which further includes socket means for holdingsaid lamp, said socket means being adapted to hold the lamp at aplurality of different axial locations along said lamp axis.
 16. Acombination according to claim 1 in which the end of the cavity oppositethe said end surface is substantially nonreflective.
 17. A combinationaccording to claim 8 in which the end of the cavity opposIte the saidend surface is substantially reflective.
 18. A combination according toclaim 1 in which the boundaries of the surfaces at the open edge of thecavity are coplanar.
 19. A combination according to claim 11 in whichthe boundaries of the surfaces at the open edge of the cavity arecoplanar.
 20. A combination according to claim 1 in which a supportholds the reflector above the ground, and the greater area ofillumination extends away from the projection of the support on theground, there further being provided a socket to receive and support thelamp, there being a socket at the end of the reflector away from thesupport, and the reflecting end section being the closer to the support.21. A combination according to claim 1 in which the socket end of thelamp is deeper in the cavity of the reflector than the free end of thelamp, and in which the socket end of the lamp is the end farther removedfrom the said end surface.
 22. A reflector for forming a field ofradiated light from a lamp of the type which emits visible light, saidlamp having an axis of radiation and the property of emitting adisproportionately large percentage of its luminus flux in an annulusbounded by a pair of surfaces of revolution generated around the axis bygenerator lines which, in an axial plane, diverge from the normal to thelamp axis by no more than about 50*, said reflector having alongitudinal axis, a central plane which includes said longitudinal axisand lamp axis, and an open, inwardly concave cavity in which the lamp isplaced, said cavity opening at a base plane parallel to the longitudinalaxis, said cavity being bounded, at least in part, by the followingreflecting surfaces: a. a cap surface which overlays the cavity, andextends generally along and transverse to said longitudinal axis; b. apair of concave side surfaces, one on each side of the central plane,intersecting the cap surface, and extending generally along saidlongitudinal axis; c. a concave end surface intersecting andinterconnecting both side surfaces and the cap surface, said surfacesbeing specularly reflective over the major portion of their areas; andmeans for supporting said lamp in the cavity, the said surfaces having abeam-forming property with respect to light emitted by the lamp, themeans being so disposed and arranged as to support the lamp so that itsaxis of radiation forms an acute angle with the longitudinal axis, andthe flux within said annulus impinges upon each of said surfaces.
 23. Areflector according to claim 22 in which the cap surface issubstantially planar.
 24. A reflector according to claim 23 in whichsome portions of the cap surface are modified by light-scatteringfacets.
 25. A reflector according to claim 22 in which the section-linesof the side and end surfaces which are formed by intersection with saidsurfaces by a plane normal both to the longitudinal axis and to saidside surfaces, and in which the section-line formed by intersection ofthe end surfaces and a plane which includes a line in said central planewhich is normal to the longitudinal axis are at least approximations toparabolas.
 26. A reflector according to claim 25 in which said sectionlines comprise the arcs of at least two circles of different radius. 27.A combination according to claim 22 in which said side surfaces aregenerated by a concave arcuate generator line lying in a plane normal tothe longitudinal axis and moved in a substantially straight lineparallel to said longitudinal axis, said generator line being at leastan approximation to a parabola.
 28. A combination according to claim 1in which the central plane is a plane of symmetry.
 29. A combinationaccording to claim 4 in which the central plane is a plane of symmetry.30. A combination according to claim 21 in which the central plane is aplane of symmetry.
 31. A reflector according to claim 22 in which thecentral plane is a plane of symmetry.
 32. A reflector according to cLaim25 in which the central plane is a plane of symmetry.